Author: Ricardo Gibert
Date: 07:46:21 08/31/99
Go up one level in this thread
On August 31, 1999 at 10:32:10, Robert Hyatt wrote: >On August 31, 1999 at 06:16:22, Ralf Elvsén wrote: > >>On August 31, 1999 at 04:51:18, Ricardo Gibert wrote: >> >>>On August 31, 1999 at 00:30:24, Howard Exner wrote: >>> >>>>On August 30, 1999 at 19:41:54, Ralf Elvsén wrote: >>>> >>>>>Some while ago I posted a position where I was >>>>>impressed by Hiarcs accurate evaluation in a pawn ending: >>>>> >>>>>6k1/1p4p1/p7/2Ppp3/1P6/P4KP1/5P1P/8 b - - 0 49 >>>>> >>>>>The fact that white can create passed pawns on >>>>>both sides of the board makes the victory clear, >>>>>and Hiarcs gave an evaluation of about +2. Note however >>>>>that white is a pawn up. >>>>> >>>>>Not being entirely convinced about the >>>>>impeccabilty of its evaluation, I decided to test >>>>>some similar "clean" positions. >>>>> >>>>>First position: >>>>> >>>>>4k3/p6p/8/4p3/3p4/3K4/PP4PP/8 b - - 0 1 >>>>> >>>>>This is (from a human point of view) an "identical" position but >>>>>with material equality. A win for white. Here Hiarcs thinks black >>>>>is slightly better! >>>>> >>>>>Second position: >>>>> >>>>>4k3/p6p/8/3p4/2p5/2K5/P4PPP/8 b - - 0 1 >>>>> >>>>>Here one pawn is moved from one side of the board to the other >>>>>(compared to the previous position) and that makes it a clear draw, >>>>>but Hiarcs thinks white has an advantage, although not decisive. >>>>>So Hiarcs thinks position 2 is better for white than position 1, >>>>>when in fact it is worse. >>>>> >>>>>I am now inclined to believe (or rather convinced...) >>>>>that Hiarcs correct score in the position from my >>>>>original post was due to the fact that white was a pawn up in a pawn ending, >>>>>(which is heavily weighted, understandably) and not from some accurate >>>>>evaluation of the pawn structure... >>>>> >>>>>Don't investigate the chess "knowledge" of your favourite chess software, >>>>>your illusions can be shattered :) >>>>> >>>>>Ralf >>>>> >>>>>PS: I always screw things up when I post positions and other stuff. >>>>>Hope I got it right this time... >>>> >>>>6k1/1p4p1/p7/2Ppp3/1P6/P4KP1/7P/8 b >>>> >>>>Here is your original position minus the white pawn on f2, >>>>so now material is equal. Like Hiarcs' eval of the original >>>>Rebel 10 also gives a big plus for white. But now in this equal material >>>>position which remains a very simple win for white, Rebel 10 thinks black is >>>>much better. It seems that only deep calculation will aid computers here >>>>while humans see this at a glance. >>> >>>Yes. Computers cannot calculate far enough to "understand" these positions. >>>Their evals are not much better than "random noise". They can do tactics & in >>>many respects positional play, but stategy (i.e. planning) is neglected, which >>>is what is needed here. To do stategy, they need to be able to generalize and >>>they don't do that. >> >>I don't know if strategy is needed. As a naive non-programmer >>I imagine that you could add something like this in the evaluation: >> >>local pawn majority (plus check for non-block e.g. >>white pawns g2, h4, black pawn h5) -> future passed pawn >> >>if (the above) on both sides of the board -> big plus in score >> >>Of course it depends on the position of the kings etc. >>Might get messy... I think Bob indicated a scheme similar to this >>in a previous post (or maybe I misunderstood him). >> >>Note that in the last positions I posted, if you let >>black have pawns on e.g. e4 and d4 and alter the location >>of the kings slightly, then black can win in some situations... >> >>Ralf > > >Note also that there is a special case crafty already handles. IE white >has pawns at g4/h5 and black has a pawn at h6. White has a 'hidden' passed >pawn because if he plays g5, he gets a passer immediately that out-runs the >opponent's passer... Writing code for each special cases does not seem practical to me. You may get some of the more common cases this way, but a more general method is needed to cope with all of them.
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